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The LEGI* Coriolis platform was used to help study the impact of ocean currents on ice melt in Antarctica. The results were published in Nature.
Several observations by satelit have confirmed that Antarctica’s ice sheet has been losing mass at a highly accelerated rate over the past couple of decades. Unlike glaciers in the Alps or Greenland, air contact ice melt is negligible in Antarctica. Instead, it is agreed that ice melt is mostly happening through contact with water. Antarctica’s land-based glaciers feed into large floating ice sheets on the ocean. Melting caused by contact with the ocean encourages further glacier flow towards the ocean.
The ice sheets around Antarctica are more than one kilometer thick and end as ice cliffs that dominate the ocean. However, ice melt has been occurring at a heterogeneous rate around the continent. As a result, a team of Swedish, Norwegian and British researchers implemented a project to better understand this phenomenon.
The importance of ocean currents
While surrounding seawater may be only a few degrees above freezing, ocean currents are sufficient to melt the underside of Antarctica’s ice sheet. This ice melt weakens the ice sheets and contributes to their break up into huge icebergs.
A better understanding of these currents helps scientists anticipate ice melt and the resulting increase in ocean levels. By the end of the century, ocean levels could increase by up to one meter. But observing this change is quite a difficult task. As a result, the researchers called upon LEGI skills in order to simulate water currents using the Coriolis platform. “This rotating tank is 13 meters wide and can reproduce a small scale version of phenomena that take place in oceans. The characteristic canyons in oceans surrounding the Antarctic region were imitated and placed at the bottom of the tank. Colored water was then injected into the tank and observed using a laser. Different density levels were tested by varying salt levels while the rotation of the tank imitated the effect of earth’s rotation,” explains Joël Sommeria, director of LEGI.
Fine-tuning ocean current models
The research results recently published in Nature enable scientists to better understand the convection and heat transfer mechanisms present in these ocean currents and how they impact currents passing under an ice sheet. “When water density is constant, the current is blocked deep under by the edge of the ice and moves around the ice sheet. When a heterogeneous liquid density was used, we observed that dense water was no longer blocked and could travel under the ice sheet.” The results from the Coriolis platform demonstrate that the quantity of water flowing under an ice sheet depends on several water current factors: speed, differences in density, and the shape of the ocean floor and ice sheet.
These results have already enabled researchers to fine-tune ocean current models and better target their measurement activities. Over the long-term, these results will help better predict the risk of a major acceleration in ice melt due to global warming.